Aggression is solely going to be based upon the individual swan's demeanor, its upbringing (i.e., was it raised with other waterfowl, which it was, etc.). The swan could become territorial and chase other waterfowl if it has a mate or cygnets. There are several issues about the concern for getting it a mate would be:

1. Are you absolutely sure that the juvenile swans is indeed a male swan Probing can be an unreliable means of ascertaining gender due to the imaturity of the genital organs. DNA Sequencing (taking blood or feather) and submitting to a licensed laboratory is more reliable.

2. Does your area require a permit to own a swan? If so, you may have an issue getting the young swan a mate as your permit may either prevent you from introducing additional swans to your area or limit the breeding of swans.

3. If you are allowed to own and maintain swans, you may still be required to have a breeder's license if you introduce a mate of opposite gender which can produce cygnets. Cygnets become a labor intensive project as they must be pinioned (rendered unable to fly at 1-3 weeks of age), vaccinated and require additional veterinary care and costs. Additionally, once the reach 6-8 months of age, the parents may chase them from the area and then you will need to find another good home for them. Mute swans can produce 1-10 cygnets a year, Black Swans can produce 1-5 cygnets twice a year. That is a lot of swans and are you ready to undertake this venture monetarily and time wise?

Finally, if you are going to find it a mate, it would be best to get a swan of the same gender (so no cygnets are produced), but you need to do it quickly and introduce a bird approximately the same age so that juvenile swans will bond and you will minimize the chance of aggression or conflict as they get older. The Regal Swan